Fiber alignment apparatus and process using cornercube offset tool

ABSTRACT

A system and method for aligning optical fibers that takes into account variations due to temperature changes and other nonrandom systemic effects. The system includes an alignment tool having a plurality of internal reflection surfaces and located below a vision plane of the first one of the pair of optical fibers, and an optical detector to receive an indirect image of a bottom surface of the first optical fiber through the alignment tool, such an offset between the first optical fiber and the optical detector is determined based on the indirect image received by the optical detector. The method comprises the steps of providing a cornercube offset tool having a plurality of total internal reflection surfaces below a vision plane of the first optical fiber, and receiving an indirect image of the first optical fiber through the cornercube offset tool.

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/912,024 filed on Jul. 24, 2001 now U.S. Pat. No. 6,412,683.

FIELD OF THE INVENTION

This invention relates generally to the use of machine vision systemsfor semiconductor chip bonding/attaching devices. More specifically, thepresent invention relates to the use of a corner cube retro-reflector asan offset alignment tool that acquires indirect images of optical fibersoptic during the alignment process when the same lie outside the view ofthe imaging system. From such images, coordinate information on positioncan be obtained and any positional offset from reference position of thefiber optic alignment tool due to deviations caused by thermal change orother nonrandom systemic errors can be taken into account for correctalignment and placement of optical fibers with respect to other opticalfibers or fiber optic detectors/devices/elements.

BACKGROUND OF THE INVENTION

The fabrication of electronic assemblies, such as integrated circuitchips and fiber optic cables, requires alignment inspection of thedevice at various phases of the fabrication process. Such alignmentinspection procedures utilize vision systems or image processing systems(systems that capture images, digitize them and use a computer toperform image analysis) to align devices and guide the fabricationmachine for correct placement and/or alignment of components.

In conventional systems, post attach inspection is used to determine ifchanges in fabrication machine position are necessary to effect properplacement and/or alignment. As such, these conventional systems can onlycompensate for misalignment after such improper alignment is made,thereby negatively effecting yield and throughput. These conventionalsystems have additional drawbacks in that they are unable to easilycompensate for variations in the system due to thermal changes, forexample, requiring periodic checking of completed devices furtherimpacting device yield and negatively impacting manufacturing time.

In conventional systems the vision system (shown in FIG. 11) consists oftwo image devices, a first image device 1104 placed below the opticalplane 1112 and views objects upward and a second image device 1102placed above the optical plane and views objects downward. Theseconventional systems have drawbacks, in that in addition to requiringmore than one image device, they are unable to easily compensate forvariations in the system due to thermal changes, for example.

SUMMARY OF THE INVENTION

In view of the shortcomings of the prior art, it is an object of thepresent invention to provide a system and method for aligning opticalfibers using a vision system that takes into account variations due totemperature changes and other nonrandom systemic effects.

The present invention is a vision system for use in aligning opticalfibers. The system comprises an alignment tool having a plurality ofinternal reflection surfaces, the alignment tool located below a visionplane of the first optical fiber; and an optical detector to receive anindirect image of a bottom surface of the first optical fiber throughthe alignment tool.

According to another aspect of the invention, the vertex of thealignment tool is located at a position about midway between the opticalaxis of the optical detector and the optical axis of the first opticalfiber.

According to a further aspect of the invention, the alignment toolcomprises a cornercube offset tool.

According to still another aspect of the invention, the focal plane ofthe vision system is positioned at or above the alignment tool.

According to yet another aspect of the present invention, the systemincludes a lens positioned between the alignment tool and i) the opticaldetector and ii) the first optical fiber.

According to still another aspect of the present invention, the systemincludes a first lens positioned between the optical detector and thealignment tool and a second lens positioned between the first opticalfiber and the alignment tool.

According to a further aspect of the present invention, the first lensand the second lens are located at or below the image plane.

According to yet a further aspect of the present invention, thereflecting surfaces are three mutually perpendicular faces.

According to yet another aspect of the present invention, the anglebetween each of the internal reflective surfaces and the top surface ofthe cornercube offset tool is about 45°.

According to still another aspect of the invention, the optical detectoris a CCD camera.

According to yet another aspect of the invention, the optical detectoris a CMOS imager.

According to yet a further aspect of the invention, the optical detectoris a position sensitive detector.

According to an exemplary method of the present invention, a cornercubeoffset tool is positioned below a vision plane of the first opticalfiber; a lens is positioned between i) the first optical fiber and thecornercube offset tool and ii) between the optical imager and thecornercube offset tool; and the first optical fiber is viewed indirectlythrough the cornercube offset tool and the lens.

These and other aspects of the invention are set forth below withreference to the drawings and the description of exemplary embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following Figures:

FIG. 1 is a perspective view of an exemplary embodiment of the presentinvention;

FIG. 2A is a side view of image ray traces according to a firstexemplary embodiment of the present invention;

FIG. 2B is a side view of image ray traces according to a secondexemplary embodiment of the present invention;

FIG. 3 is a perspective view of image ray traces according to anexemplary embodiment of the present invention;

FIGS. 4A and 4B are perspective and side views, respectively, of anexemplary embodiment of the present invention;

FIG. 5 illustrates the telecentricity of an exemplary embodiment of thepresent invention;

FIG. 6 is a detailed view of an exemplary retroreflective cornercubeoffset tool according to the present invention;

FIGS. 7A-7C illustrate the effect of tilt about the vertex of thecornercube tool of the exemplary vision system;

FIGS. 8A-8C illustrate the effect of tilt about the X and Y axis of theexemplary vision system;

FIG. 9 is a side view of image ray traces according to a third exemplaryembodiment of the present invention;

FIGS. 10A-10E are various views of a fourth exemplary embodiment of thepresent invention;

FIG. 11 is a vision system according to the prior art;

FIG. 12 is an illustration of a fifth exemplary embodiment of thepresent invention; and

FIGS. 13A-13D are various views of a sixth exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION

The entire disclosure of U.S. patent application Ser. No. 09/912,024filed on Jul. 24, 2001 is expressly incorporated by reference herein

Referring to FIG. 1 a perspective view of an exemplary embodiment of thepresent invention is shown. The system is included in wire bondingmachine 100, and employs a cornercube 106, having a plurality ofinternal reflection surfaces (best shown in FIG. 6), located at or belowimage plane 112 of bonding tool 104.

In an exemplary embodiment, cornercube offset alignment tool 109(comprising cornercube 106 and lens elements 108, 110), has a total ofthree internal reflection surfaces, 218, 220, and 221 (best shown inFIG. 6 and described below). In another exemplary embodiment, cornercube106 may have a plurality of total internal reflective surfaces. In oneexemplary embodiment, cornercube 106 is formed from fused silica,sapphire, diamond, calcium fluoride or other optical glass. Note,optical quality glass, such as BK7 made by Schott Glass Technologies ofDuryea, Pa., may also be used. Note also that materials for cornercube106 can be selected for maximum transmission with respect to the desiredoperating wavelength.

Optical imaging unit 102, such as a CCD imager, CMOS imager or a camera,for example, is mounted above image plane 112 in order to receive anindirect image of bonding tool 104 through cornercube offset alignmenttool 109. In another exemplary embodiment, a position sensitive detector(PSD), such as that manufactured by Ionwerks Inc., of Houston, Tex., mayalso be used as optical imaging unit 102. In such an embodiment, whenthe hole in bonding tool 104 is illuminated, such as by using an opticalfiber for example, the PSD can be utilized to record the position of thespot of light exiting bonding tool 104. It is also contemplated that thePSD may be quad cell or bi-cell detector, as desired.

In the exemplary embodiment, the focal point of the vision system(coincident with imaginary plane 211 shown in FIG. 2A) is located abovebottom surface 223 (shown in FIG. 2A) of cornercube 106. In addition,the exemplary embodiment includes two preferably identical lens elements108, 110 located at or below image plane 112. Another embodiment, shownin FIG. 2B, includes a single lens element 205 located below image plane112 and in line with optical axes 114, 116. Hereinafter, the combinationof cornercube offset tool 106, and lens elements 108, 110 (or lenselement 205) will be referred to as assembly 109.

Image plane 112 of cornercube 106, including lens elements 108, 110, ispositioned at the object plane of optical imaging unit 102. In otherwords, the object plane of cornercube 106 and lens elements 108, 110 arealigned to bonding tool 104 which also lies in image plane 112. In theexemplary embodiment, lens elements 108, 110 (or 205) preferably have aunitary magnification factor. First lens element 108 is positioned in afirst optical axis 114 between bonding tool 104 and cornercube 106.Second lens element 110 is substantially in the same plane as that offirst lens element 108 and is positioned in a second optical axis 116between optical imaging unit 102 and cornercube 106. In one exemplaryembodiment, first and second optical axes 114 and 116 are substantiallyparallel to one another, and are spaced apart from on another based onspecific design considerations of bonding machine 100. In one exemplaryembodiment the distance 118 between first optical axis 114 and secondoptical axis 116 is about 0.400 in. (10.160 mm.) although distance 118may be as small as about 0.100 in. (2.54 mm) depending on designconsiderations related to the bonding machine.

FIG. 2A is a detailed side view of image ray traces and illustrates thegeneral imaging concept of an exemplary embodiment of the presentinvention. In FIG. 2A, exemplary ray traces 210, 214 are separated forclarity to illustrate the relative immunity of the resultant image dueto positional changes. The same distance also separates the image pointsbecause lens elements 108, 110 serve as unitary magnification relays.FIG. 2A also demonstrates how changes in the bonding tool 104 positionare compensated for. For example, once conventional methods have beenused to accurately measure the distance between imaging unit 102 andbonding tool 104 (shown in FIG. 1), the present invention is able tocompensate for changes in the bonding tool 104 offset position 222 dueto changes in the system. The location of bonding tool 104 can beaccurately measured because cornercube offset tool 106 images bondingtool 104 onto image plane 112 of the optical system.

The reference position of bonding tool 104 is shown as a reflected raywhich travels from first position 202 along first optical axis 114(shown in FIG. 1), as direct image ray bundle 210 from first position202 through first lens element 108. Direct image ray bundle 210continues along first optical axis 114 where it then passes through topsurface 226 of cornercube 106 onto first internal reflection surface218. Direct image ray bundle 210 is then reflected onto second internalreflection surface 220, which in turn directs it onto third internalreflective surface 221 (best shown in FIG. 3). Next, direct image raybundle 210 travels back through top surface 226 of cornercube 106 asreflected image ray bundle 212 along the second optical axis 116 (shownin FIG. 1) and through second lens element 110 to image plane 112. It isreflected image ray bundle 212 that is detected by imaging unit 102 asimage 204.

Consider now that the position of bonding tool 104 is displaced by adistance 222 due to a variation in system temperature, for example. Asshown in FIG. 2A, the displaced image of bonding tool 104 is shown asposition 206 and imaged along the path of second position ray trace 214.As shown in FIG. 2A, direct image ray bundle 214 travels along a pathsimilar to that of direct image ray bundle 210 from first position 202.Second position 206 image travels as a direct image ray bundle 214,through first lens element 108. Direct image ray bundle 214 then passesthrough top surface 226 of cornercube 106 onto first internal reflectionsurface 218. Direct image ray bundle 214 is then reflected onto secondinternal reflection surface 220, which in turn directs it onto thirdinternal reflection surface 221 (best shown in FIG. 3). Next, directimage ray bundle 214 travels through top surface 226 of cornercube 106as reflected image ray bundle 216 and through second lens element 110 toimage plane 112. Reflected image ray bundle 216 is viewed as a reflectedimage by imaging unit 102 as being in second position 208. Although theabove example was described based on positional changes along the Xaxis, it is equally applicable to changes along the Y axis.

As illustrated, the original displacement of bonding tool 104, shown asoffset position 222, is evidenced by the difference 224 in the measuredlocation of bonding tool 104 at second position 208 with respect toreference location 204. As evidenced by the above illustration, apositional shift in assembly 109 does not affect the reflected image asviewed by imaging unit 102. In other words, assembly 109 of the presentinvention may be translated along one or both the X and Y axes such thatthe image of the bonding tool 104 appears relatively stationary toimaging unit 102. There will be some minimal degree of error, however,in the measured position of bonding tool 104 due to distortion in thelens system (discussed in detail below).

Referring again to FIG. 2A, vertex 228 (shown in phantom) of cornercubeoffset alignment tool 109 is located at a position approximately midwaybetween first optical axis 114 and second optical axis 116. Tofacilitate mounting of cornercube 106, a lower portion 235 of thecornercube may be removed providing bottom surface 223, which may besubstantially parallel to top surface 226. Removal of lower portion 235does not affect the reflection of image rays since the image raysemanating from image plane 112 do not impinge upon bottom surface 223.

Exemplary cornercube 106 comprises top surface 226, first reflectivesurface 218, bottom surface 223, second reflective surface 220, andthird reflective surface 221. If top surface 226 is set such thatoptical axes 114, 116 are normal to top surface 226, first reflectivesurface 218 will have a first angle 230 of about 45° relative to topsurface 226, and a second angle 234 of about 135° relative to bottomsurface 223. Likewise, ridgeline 225 (formed by the intersection ofsecond and third reflective surfaces 220 and 221) has similar angles 232and 236 relative to top surface 226 and bottom surface 223,respectively. In addition, second and third reflective surfaces 220 and221 are orthogonal to one another along ridgeline 225. In the exemplaryembodiment, bottom surface 223 of cornercube 106 may be used as amounting surface if desired. It should be noted, however, that it is notnecessary to form top surface 226 so that the image and reflected raysare normal thereto. As such, the corner cube will redirect the incidentlight or transmit image of bonding tool 104 parallel to itself with anoffset equal to 118.

The present invention can be used with light in the visible, UV and IRspectrum, and preferably with light having a wavelength that exhibitstotal internal reflection based on the material from which cornercube106 is fabricated. The material selected to fabricate cornercube offsetalignment tool 109 is based on the desired wavelength of light which thetool will pass. It is contemplated that cornercube offset alignment tool109 may be fabricated to handle a predetermined range of lightwavelengths between the UV (1 nm) to the near IR (3000 nm). In apreferred embodiment, the range of wavelength of light may be selectedfrom between about i) 1 and 400 nm, ii) 630 and 690 nm, and iii) 750 and3000 nm. Illumination may also be provided by ambient light or by theuse of an artificial light source (not shown). In one exemplaryembodiment, typical optical glass, having an index of refraction of 1.5to 1.7, may be used to fabricate cornercube 106. Note, the index ofrefraction is based upon the material chosen for maximum transmission atthe desired operating wavelength. In one embodiment, cornercube offsetalignment tool 109 has an index of refraction of about 1.517.

FIG. 3 is a perspective view of image ray traces according to anexemplary embodiment of the present invention translated in a directionperpendicular to the separation of lens elements 108, 110. The sameimage properties shown in FIG. 2A are also evident in FIG. 3. Forexample, the reference position of bonding tool 104 is represented byfirst position 302 and its image 304 is viewed as a first direct imageray 310 which travels along first optical axis 114 through first lenselement 108; passes through top surface 226 of cornercube 106; strikesfirst reflective surface 218 of cornercube 106; travels throughcornercube 106 in a path parallel to top surface 226; strikes secondreflective surface 220; strikes third reflective surface 221 beforeexiting the cornercube 106 through top surface 226 and travels alongsecond optical axis 116 through second lens element 110 onto image plane112 and viewed by imaging unit 102 at position 304. Positionaldisplacement of bonding tool 104 is also shown in FIG. 3 and isillustrated by the path of the ray traces 314, 316 from second position306 to second viewed position 308.

FIGS. 4A-4B are perspective and side views, respectively, of anexemplary embodiment of the present invention illustrating lens elements108, 110 and cornercube 106. The two lens elements 108, 110 (or 205) arepreferably doublets located above the cornercube 106 based on theirfocal distance from image plane 112 and imaginary plane 211. Doubletsare preferred based on their superior optical qualities. As illustratedin FIGS. 4A-4B, an exemplary embodiment of cornercube 106 has threeinternal reflective surfaces, 218, 220 and 221. As shown in FIG. 4B, theexterior edges of lens elements 108, 110 and cornercube 106 arecoincident with one another.

FIG. 5 illustrates the telecentricity of an exemplary embodiment of theimage system of the present invention. As shown in FIG. 5, lens elements108, 110 produce a unitary magnification and are arranged relative tocornercube 106 such that the telecentricity of the machine vision systemis maintained. Note that front focal length 502 from lens element 108 tovertex 228 of cornercube 106 is equal to front focal 502 from lenselement 110 to vertex 228 of cornercube 106. Note also, that back focallength 504 from lens element 108 to image plane 112 is equal to backfocal length 504 from lens element 110 to image plane 112.

FIG. 6 is a detailed view of an exemplary cornercube 106 of the presentinvention. Note that internal reflection surface, 218 and ridgeline 225allow an image of bonding tool 104 to be translated in the X and Ydirections. Note also, that the surfaces of cornercube 106 arepreferably ground so that a reflected beam is parallel to the incidentbeam to within 5 arc seconds.

As shown in FIG. 6, surfaces 220 and 221 are orthogonal to one anotheralong ridgeline 225. In addition, the angle between ridgeline 225 andsurface 218 is about 90°. Furthermore, surface 218 and ridgeline form anangle of 45° relative to top surface 226 and bottom surface 223. Notealso, that surfaces, 218, 220, and 221 meet to form triangular shapedbottom surface 223, which may be used to facilitate mounting ofcornercube 106.

FIGS. 7A-7C illustrate the effect of tilt about the orthogonal ofcornercube offset alignment tool 109 in an exemplary vision system. FIG.7A is an overhead view of lens elements 108, 110 and cornercube 106.Exemplary image origins, 702, 704, 706, and 708 correspond to theposition of image ray traces 210, 214 (shown in FIG. 2A). Note thatoptic axis position 710 corresponds to the position where the image ofbonding tool 104 (shown in FIG. 1) would be if cornercube 106 was nottilted along the Z axis.

FIGS. 7B-7C are graphs of the effect of tilt around the Z axis in termsof tilt in arc minutes vs. error in microns. FIG. 7B shows the effect oftilt around the Z axis versus error and image location along the Y axis.FIG. 7C shows the effect of tilt around the Z axis versus error andimage location along the X axis.

FIGS. 8A-8C illustrate the effect of tilt about the X and Y axis of theexemplary vision system. FIG. 8A is an additional side view of exemplaryimage ray traces 210, 212, 214, 216. In FIG. 8A, arrow 804 and dot 802are used to depict the X and Y axes, respectively.

FIGS. 8B-8C are graphs of the effect of tilt around the X and Y axes interms of tilt in arc minutes vs. error in microns. FIG. 8B shows theeffect of tilt around the X axis versus error and image location alongthe Y axis. FIG. 8C shows the effect of tilt around the Y axis versuserror and image location along the X axis.

FIG. 9 is a detailed side view of image ray traces according to a thirdexemplary embodiment of the present invention. In FIG. 9, the referenceposition of bonding tool 104 is shown as a reflected ray which travelsfrom first position 914 (on image plane 112) along first optical axis114 (shown in FIG. 1), as direct image ray bundle 922 from firstposition 914 through lens element 902. Note that in this exemplaryembodiment, lens element 902 has a relatively planar, upper surface 904and a convex lower surface 906. Direct image ray bundle 922 continuesalong first optical axis 114 where it then passes through upper surface904 of lens element 902, and in turn through convex surface 906. Directimage ray bundle 922 is then reflected onto total reflective surface908. In a preferred embodiment, total reflective surface 908 is amirror. Next, direct image ray bundle 922 travels back through lenselement 902 as reflected image ray bundle 920 along second optical axis116 (shown in FIG. 1) and onto image plane 112. It is reflected imageray bundle 920 that is detected by imaging unit 102 (shown in FIG. 1) asimage 912. Similarly, positional displacement of bonding tool 104 isalso shown in FIG. 9 and is illustrated by the path of direct image raybundles 918, 924 from second position 910 to second viewed position 916.

FIGS. 10A-10E illustrate a further embodiment of the present invention.In this exemplary embodiment, a cornercube alignment tool is used toimprove the accuracy of alignment of fibers, such as optical fibers 1008and 1009. As in the previous exemplary embodiment, the use of a cornercube offset tool allows for the use of a single optical detector insteadof the conventional multiple detector systems.

Referring to FIG. 10A, the exemplary embodiment includes cornercube1014, lenses 1016, 1018, dark field illumination systems 1020, 1021(which are well known to those practicing the art) to illuminate thefiber cladding edge 1010, 1011 of fiber cores 1012, 1013, respectively(which in turn produces reflections 1024, 1025 to outline cladding edges1010, 1011), and optical detector 1002. In this exemplary embodiment,downward facing fiber 1008 is viewed by downward looking opticaldetector 1002, such as a camera (i.e., a substrate camera). Downwardlooking optical detector 1002 detects the emission of light 1022 fromfiber core 1012 and is then be able to determine the proper offset 1027between the optical fiber centerline 1023 and central ray 1029 ofdownward looking optical detector 1002. As is further shown in FIG. 10A,downward facing fiber 1008 and optical detector 1002 are offset from oneanother by predetermined distance 1006.

FIG. 10B is a plan view of the exemplary embodiment illustrated in FIG.10A illustrating the relative positions of lenses 1016 and 1018, andcornercube 1014.

In FIG. 10C, downward looking optical detector 1002 and downward facingfiber 1008 are then repositioned such that central ray 1029 of downwardlooking optical detector 1002 is aligned with fiber centerline 1031 ofupward facing fiber 1009. Once again dark field illumination system 1021is used to illuminate upward facing fiber 1009 for recognition by thevision system to ensure proper alignment with optical detector 1002.

Next, and as shown in FIG. 10D, optical detector 1002 and downwardfacing fiber 1008 are again repositioned based on the offset 1027determined during the process discussed above with respect to FIG. 10A.As a result downward facing fiber 1008 and upward facing fiber 1009 arealigned with one another.

As shown in FIG. 10E, optical fibers 1008 and 1009 are then joined usingconventional techniques, such as fusing the fibers together usingradiation (not shown), or mechanical means, for example.

FIG. 12 illustrates yet a further embodiment of the present invention.In this exemplary embodiment, a cornercube alignment tool is used toalign individual fibers (sub-fibers) 1202 a of a fiber optic splitter1200 with respective individual optical fibers 1008, etc. As in theprevious exemplary embodiment, the use of a corner cube offset toolallows for the use of a single optical detector instead of theconventional multiple detector systems. As the steps leading up toalignment and coupling of optical fiber 1008 and sub-fiber 1202 aresimilar to the above exemplary embodiment, they are not repeated here.

Once the first sub-fiber is aligned with single fiber 1008, the processis repeated for a further sub-fiber, such as 1202 b, and another singlefiber (not shown).

Of course the exemplary embodiment is not limited to the fiber opticbundle of a fiber optic splitter being below optical detector 1002. Theembodiment also contemplates that the relative positions of fiber opticbundle 1200 and optical fiber 1008 are reversed, such that fiber opticbundle 1200 is positioned above cornercube 1014.

FIGS. 13A-13D illustrate a further embodiment of the present invention.In this exemplary embodiment, a cornercube alignment tool is used toimprove the accuracy of alignment of an optical fiber 1008 with acircuit element, such as a detector 1302. In FIG. 13A, exemplarydetector 1302 is part of an array 1300, although the invention is not solimited. It is also contemplated that circuit element 1302 may be adiode, such as a photodiode or an emitter of optical radiation. As inthe previous exemplary embodiments, the use of a corner cube offset toolallows for the use of a single optical detector instead of theconventional multiple detector systems.

Referring to FIG. 13A, the exemplary embodiment includes cornercube1014, lenses 1016, 1018, dark field illumination system 1020 (which iswell known to those practicing the art) to illuminate the fiber claddingedge 1010 of fiber core 1012 (which in turn produces reflections 1024 tooutline cladding edge 1010), and optical detector 1002. In thisexemplary embodiment, downward facing fiber 1008 is viewed by downwardlooking optical detector 1002, such as a camera (i.e., a substratecamera). Downward looking optical detector 1002 detects the emission oflight 1022 from fiber core 1012 and is then be able to determine theproper offset 1027 between the optical fiber centerline 1023 and centralray 1029 of downward looking optical detector 1002. As is further shownin FIG. 10A, downward facing fiber 1008 and optical detector 1002 areoffset from one another by predetermined distance 1006.

In FIG. 13B, downward looking optical detector 1002 and downward facingfiber 1008 are then repositioned such that central ray 1029 of downwardlooking optical detector 1002 is aligned with optical centerline 1304 ofdetector 1302. It is understood that optical centerline 1304, may notnecessarily coincide with the physical center of detector 1302, butrather is dependant on the layout of the particular detector 1302. Inthis case the determination of optical centerline 1304 may beaccomplished by the location of the center of the active sensing area ofthe detector.

Next, and as shown in FIG. 13C, optical detector 1002 and downwardfacing fiber 1008 are again repositioned based on the offset 1027determined during the process discussed above with respect to FIG. 13A.As a result downward facing fiber 1008 and detector 1302 are alignedwith one another. As shown in FIG. 13D, optical fiber 1008 and detector1302 are then kept in aligned position using conventional techniques,such as optical epoxies, UV epoxies, for example.

Although the invention has been described with reference to exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed to include other variants and embodiments of theinvention, which may be made by those skilled in the art withoutdeparting from the true spirit and scope of the present invention.

What is claimed:
 1. A system for aligning a pair of optical fibers, thesystem comprising: an alignment tool having at least two reflectivesurfaces and located below a vision plane of a first one of the pair ofoptical fibers; and an optical detector to receive an indirect image ofa bottom surface of the first one of the pair of optical fibers throughthe alignment tool.
 2. The system according to claim 1, wherein anoffset between the first one of the pair of optical fibers and theoptical detector is determined based on the indirect image of the firstone of the pair of optical fibers received by the optical detector. 3.The system according to claim 1, wherein the alignment tool is acounercube offset alignment tool.
 4. The system according to claim 1,wherein optical detector is positioned above a top surface of thealignment tool.
 5. The system according to claim 1, wherein thealignment tool is formed from one of fused silica, sapphire, diamond,calcium fluoride and an optical glass.
 6. The system according to claim1, wherein the optical detector is a camera.
 7. The system according toclaim 6, wherein the camera is a CCD camera.
 8. The system according toclaim 1, wherein the optical detector is a CMOS imager.
 9. The systemaccording to claim 1, wherein a vertex of the alignment tool is locatedat a position about midway between an optical axis of the opticaldetector and an optical axis of the first optical fiber.
 10. The systemaccording to claim 9, wherein a focal plane of the system is positionedabove the vertex of the alignment tool.
 11. The system according toclaim 1, further comprising: a lens disposed between the alignment tooland i) the optical detector and ii) the first one of the pair of opticalfibers.
 12. The system according to claim 11, wherein the lens is a pairof lenses, a first lens of the pair of lenses disposed between thealignment tool and the optical input means and a second lens of the pairof lenses disposed between the alignment tool and the first opticalfiber.
 13. The system according to claim 11, wherein the lens has aunitary magnification factor.
 14. The system according to claim 1,wherein the alignment tool has an apex angle of about 90° and a secondangle of about 45°.
 15. The system according to claim 1, wherein thesystem is used with light having a wavelength in the visible spectrum.16. The system according to claim 1, wherein the system is used withlight having a wavelength between about 1-3000 nm.
 17. The systemaccording to claim 1, wherein the system is used with light having awavelength between about 630-690 nm.
 18. The system according to claim1, wherein the system is used with light having a wavelength betweenabout 1-400 nm.
 19. The system according to claim 1, wherein the systemis used with light having a wavelength between about 700-3000 nm. 20.The system according to claim 1, wherein the system is used with lighthaving a wavelength of about 660 nm.
 21. The system according to claim1, further comprising: a lens positioned in both i) a first optical axisbetween the optical detector and the alignment tool and ii) a secondoptical axis between the first optical fiber and the alignment tool,wherein the first and second optical axis are substantially parallel toone another.
 22. The system according to claim 1, wherein the alignmenttool has a plurality of internal reflection surfaces.
 23. A system foraligning a pair of optical fibers, the system comprising: an alignmenttool having at least two reflective surfaces and located below a visionplane of a first one of the pair of optical fibers; and an opticaldetector to receive i) an indirect image of a bottom surface of thefirst one of the pair of optical fibers through the alignment tool andii) a direct image of a top section of a second one of the pair ofoptical fibers.
 24. The system according to claim 23, wherein the atleast two reflective surfaces are a plurality of internal reflectionsurfaces.
 25. A vision system for use with an optical detector foraligning a pair of optical fibers, the system comprising: a cornercubeoffset tool located below a vision plane of a first one of the pair ofoptical fibers; and a lens positioned in both i) a first optical axisbetween the vision plane and the cornercube offset tool and ii) a secondoptical axis between the optical detector and cornercube offset tool,wherein the optical detector receives at least an indirect image of thefirst one of the pair of optical fibers through the cornercube offsettool.
 26. The cornercube offset tool according to claim 25, wherein thecornercube offset tool has a plurality of internal reflection surfaces.27. The cornercube offset tool according to claim 25, wherein theplurality of internal reflection surfaces are three internal reflectionsurfaces.
 28. A vision system according to claim 25, wherein the opticaldetector is positioned above the image plane.
 29. A vision systemaccording to claim 25, wherein the first optical axis and the secondoptical axis are substantially parallel to one another.
 30. The deviceaccording to claim 25, wherein the lens has a unitary magnificationfactor.
 31. The device according to claim 25, wherein the lens is afirst lens positioned in the first optical axis and a second lenspositioned in the second optical axis.
 32. The device according to claim31, wherein the first lens and the second lens each have a unitarymagnification factor.
 33. A vision system for aligning optical fibers,the system comprising: a cornercube offset tool having at least tworeflective surfaces and located below a vision plane of the system; andan optical detector to receive an indirect image of the first one of thepair of optical fibers through the cornercube offset tool, wherein theoptical fibers are aligned with one another based on i) the indirectimage of a first one of the optical fibers and ii) a direct image of asecond one of the optical fibers received by the optical detector.
 34. Avision system according to claim 33, wherein the cornercube offset toolhas three internal reflection surfaces.
 35. A vision system according toclaim 33, wherein at least one of the reflection surfaces is a totalinternal reflection surface.
 36. A vision system according to claim 33,wherein the plurality of internal reflection surfaces are total internalreflection surfaces.
 37. A system for aligning optical fibers, thesystem comprising: image redirecting means having at least tworeflective surfaces and disposed below a vision plane of a first one ofthe optical fibers; and detecting means to receive an indirect image ofa bottom surface of the first one of the optical fibers through theimage redirecting means, wherein the first optical fiber is aligned witha second optical fiber based on the indirect image received by thedetecting means.
 38. The system according to claim 37, wherein the atleast two reflective surfaces are a plurality of internal reflectionsurfaces.
 39. A method for aligning a pair of optical fibers, the methodcomprising the steps of: providing a cornercube offset tool below avision plane of a first one of the pair of optical fibers; viewing anindirect image of the first one of the pair of optical fibers with anoptical detector through the cornercube offset tool; determining anoffset between the first one of the pair of optical fibers and theoptical detector based on the indirect image; and aligning the first oneof the pair of optical fibers with a second one of the pair of opticalfibers based on the offset.
 40. The method according to claim 39,further comprising the steps of: reflecting internally an image of thefirst one of the pair of optical fibers, and providing the internallyreflected image for viewing by the optical detector.
 41. A system foraligning a pair of optical fibers, the system comprising: a cornercubeoffset tool having a plurality of internal reflection surfaces, thecornercube offset tool located below a vision plane of a first one ofthe pair of optical fibers; and an optical detector to receive anindirect image of the first one of the pair of optical fibers throughthe cornercube offset tool, wherein an offset between the first one ofthe pair of optical fibers and the optical detector is determined basedon the indirect image of the first one of the pair of optical fibers.42. The system according to claim 41, wherein the optical detectordetermines a position of a second one of the pair of optical fibersbased on receiving a direct image of the second one of the pair ofoptical fibers.
 43. The system according to claim 41, further comprisingrespective ones of an illumination system to illuminate a respectivefiber cladding of each of the pair of optical fibers.
 44. The systemaccording to claim 41, wherein the optical detector is positioned abovean upper surface of the cornercube offset tool.
 45. A system foraligning a pair of optical fibers, the system comprising: imageredirecting means disposed below a vision plane a first one of the pairof optical fibers, the image redirecting means having a plurality ofinternal reflection surfaces; and detecting means to receive an indirectimage of the first one of the pair of optical fibers through the imageredirecting means, wherein an offset between the first one of the pairof optical fibers and the detecting means is determined based on theindirect image of the first one of the pair of optical fibers.
 46. Amethod for use with an optical imager to align a pair of optical fibers,the method comprising the steps of: providing a cornercube offset toolbelow an end of a first one of the pair of optical fibers, thecornercube offset tool having three internal reflection surfaces;viewing an indirect image of the end of a first one of the pair ofoptical fibers with the optical imager through the cornercube offsettool; determining an offset distance of the first one of the pair ofoptical fibers; viewing a direct image of an end of a second one of thepair of optical fibers with the optical imager; and aligning the firstone of the pair of optical fibers with the second one of the pair ofoptical fibers.
 47. A system for aligning a plurality of optical fiberscontained in a fiber optic splitter bundle, the system comprising: analignment tool located below a vision plane of the fiber optic bundle;and an optical detector to receive an indirect image of a bottom surfaceof at least one of the plurality of optical fibers through the alignmenttool.